1. Technical Field
This application relates to UMTS (Universal Mobile Telecommunications System) in general, and to an apparatus and method for taking measurements in universal mobile telecommunications system user equipment.
2. Description of the Related Art
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In a typical cellular radio system, mobile user equipment (UE) communicates via a radio access radio network (RAN) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
UMTS is a third generation public land mobile telecommunication system. Various standardisation bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardisation body, specific partners publish and set standards in their respective areas.
Consider a wireless mobile device, generally referred to as user equipment (UE), that complies with the 3GPP specifications for the UMTS protocol. The 3GPP 25.331 specification, v.3.16.0, referred to herein as the 25.331 specification, addresses the subject of the Radio Resource Control (RRC) protocol specification. The 3GPP 25.304 specification, v.3.16.0, referred to herein as the 25.304 specification, addresses the subject of UMTS User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE. The 3GPP 25.302 specification, v.3.16.0, referred to herein as the 25.302 standard, addresses the subject of services provided by the physical layer of UTRA to upper layers.
A UE undertakes frequent measurement procedures. Clause 8.4 of the 25.331 standard and its sub-clauses and clause 14 and its sub-clauses relate to the measurement procedures to be undertaken by the UE as do clause 5.2.3.1a and its sub-clauses of the 25.304 specification. The 25.331 standard (and in particular clauses Clause 8.4 and its sub-clauses and clause 14 and its sub-clauses), the 25.304 standard (and in particular clauses 5.2.3.1 and its sub-clauses) and the 25.302 standard are incorporated herein by reference.
A UTRAN requires a UE to make measurements of its environment (for example the signal strength received from the UTRAN) and report this data back to the UTRAN so that it may control the UEs appropriately. The UTRAN instructs the UE which measurements it is required to make by sending it a MEASUREMENT CONTROL command. This command is detailed in the 25.331 standard, clause 8.4.1.
It is specified that the MEASUREMENT CONTROL command has three commands:                Set-up—The UE must initialise the measurement and start taking results.        Modify—The UE must change the measurement settings and continue to take results.        Release—The UE must stop taking measurements and delete the measurement settings.        
It is also specified that certain measurements are only valid when the UE is in certain states. For example an Intra-frequency measurement is only valid when the UE is in state Cell_DCH. If the UE moves from Cell_DCH to Cell_FACH, then the UE must stop taking the intra-frequency measurements. However, the measurement settings must be retained in the UE because when the UE returns to Cell_DCH, then it must resume taking the intra-frequency measurements again (provided that in the meantime, the UTRAN has not issued a Release command). Conventionally these measurement settings are retained in the RRC layer but the Layer 1 does not retain any measurement settings.
In a UE, it is the RRC layer which receives the UTRAN MEASUREMENT CONTROL command and instructs the Layer 1 to set-up, change or release any particular measurement. The UE is required to stop and restart the measurement without further commands from the UTRAN. For instance, the RRC may change state very briefly (for instance to send a Cell Update message) and then return to the original state. This necessitates a Release command followed by a Set-up command.
The interface between the RRC and layer 1 is described in 3GPP specification TS25.302 v3.16.0, clauses 10.2.1.3 and 10.2.1.4. Although there are no commands specified in this document, it is natural to use the same set of commands as used in the UTRAN-UE interface.
The Layer 1 does not know what state the UE is in and, for instance, when moving from Cell_DCH to Cell_FACH, the RRC must instruct the Layer 1 to stop taking the measurements and so would use a Release command. When the UE moves back to Cell_FACH, the RRC must tell the Layer 1 to start taking measurements again and so uses the Set-up command.
This results in all the settings for the measurement being sent again to the Layer 1 and the Layer 1 having to initialise the measurement again before any results can be taken.
There are thus proposed strategies for User Equipment (UE) measurement procedures and in particular the RRC protocol. A number of such strategies are detailed below.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of an apparatus and method for carrying out User Equipment (UE) measurements in connected mode.
The same reference numerals are used in different figures to denote similar elements.